* Cultural diffusion: As the Aryans migrated and settled in different regions, they came into contact with other cultures and religions. This led to the exchange of ideas and beliefs, and the eventual assimilation of some foreign elements into Aryan religion. For example, the Aryans adopted the concept of reincarnation from the Dravidians, a non-Aryan people who inhabited India before the arrival of the Aryans.
* Political changes: The political landscape of the Aryan region was constantly changing, as different kingdoms and empires rose and fell. These political changes often had a significant impact on religion. For example, the rise of the Mauryan Empire in the 3rd century BCE led to the spread of Buddhism throughout India, as the Mauryan emperor Ashoka was a Buddhist.
* Religious syncretism: Syncretism is the blending of different religious beliefs and practices. This was a common occurrence in the Aryan region, as different religious traditions came into contact with each other. For example, the Aryan god Indra was often identified with the Dravidian god Shiva.
These are just some of the factors that contributed to the changes in Aryan religion over time. It was a complex and multifaceted process, and the resulting religious landscape was a reflection of the diverse cultural, political, and religious influences that shaped the Aryan world.